Typically, as handsets and digital still cameras have gotten smaller and smaller in size, there have always been challenges to try to improve their optical performance. Accordingly, the methodology requires more accurate optical image stabilization as the cameras increase in the number of pixels per image. That means the camera module must be able to control blurring of an image due to hand jitter when taking picture as picture resolution increases. In addition a camera module must be robust and have a high tolerance to shock and vibration. In addition the module must be made as small as possible and provide significant integration to allow its use in a variety of environments. Finally the cost of the camera module must be as small as possible to allow its incorporation in various types of handsets. At the present time, no system addresses all of these criteria in an adequate manner. That is, heretofore no system provides for the integration of components required at a low cost and also provides for a robust design. To describe some of the issues with conventional camera modules refer now to the following description in conjunction with the accompanying figures.
FIGS. 1A and 1B are top and side views respectively of a conventional camera module 10. Referring to both figures, the camera module 10 includes a voice coil motor (VCM) 12, a dual axis gyroscope 14, an image sensor 16 within the module 10, a Hall element 18, and an optical image stabilization (OIS) controller 20 coupled to the image sensor 16 and the Hall element 18.
As is seen, the image sensor 16 is located within the module 10. The dual axis gyro 14, the at least one Hall element 18 and the OIS controller 20 are all located outside the module 10. In addition the at least one Hall element 18 is used as position feedback sensor in the image stabilization for the module 10.
FIG. 1C is a block diagram representation of the camera module 10 of FIGS. 1A and 1B. As is seen in FIG. 1C, the dual axis gyroscope 14 transfers the rotational motion of the camera into electronic signal and this angular velocity signal is sampled into digital signal and is further processed into camera position signal via the DSP module 22, which will be used by the OIS controller 20. The OIS controller 20 also takes the lens module position sensor signal from the path of Hall element 18 and its amplifier 26. Then the position signal from Hall element is compared with that from Gyro to generate the error signals. This error signal is sent to the actuator driver 24, then to VCM actuator 24 to make a correction motion for lens module.
This approach has several problems. The use of a Hall element 18 requires a significant amount of additional hardware and circuitry. For example, there is circuitry required to excite the Hall element 18 when there is a change in position and there is also circuitry required to sense the change of the Hall element 18 in position. In addition, the control algorithms required to control the module are relatively complex and require separate hardware.
Accordingly, the Hall element and its associated circuitry provide a level of complexity to the design that affects the cost and the performance of the module during image stabilization. Therefore it is desirable to provide an OIS controller for a camera module that addresses all criteria related to improving their performance that is small in size, having increased optical image stabilization, being very robust and being low in cost. Presently conventional camera modules do not address all four of these criteria in an effective manner.
Accordingly, what is desired is to provide an optical image stabilization method and system in a camera module which would overcome the above-identified issues. The method and system should be easy to implement, cost-effective, and adaptable to existing systems. The present invention addresses such a need.